ABSTRACT
We tried to detect C. burnetii in market chicken eggs and mayonnaise by nested PCR assay. The PCR target was the com 1 gene of C. burnetii. The positive rate for egg and mayonnaise samples was 4.2% and 17.6%, respectively. Direct sequence of some of the positive egg samples shows mutations whereas no mutation was found in the positive mayonnaise samples. The number of molecules of the Q fever agent is estimated at 10(4) to 10(6) per egg, according to our quantitative PCR test.
Subject(s)
Coxiella burnetii/isolation & purification , Eggs/microbiology , Food Microbiology , Coxiella burnetii/genetics , Food Handling/methods , Polymerase Chain ReactionABSTRACT
Cells of "Paenibacillus fukuinensis" D2 produced chitosanase into surrounding medium, in the presence of colloidal chitosan or glucosamine. The gene of this enzyme was cloned, sequenced, and subjected to site-directed mutation and deletion analyses. The nucleotide sequence indicated that the chitosanase was composed of 797 amino acids and its molecular weight was 85,610. Unlike conventional family 46 chitosanases, the enzyme has family 8 glycosyl hydrolase catalytic domain, at the amino-terminal side, and discoidin domain at the carboxyl-terminal region. Expression of the cloned gene in Escherichia coli revealed beta-1,4-glucanase function, besides chitosanase activity. Analyses by zymography and immunoblotting suggested that the active enzyme was, after removal of signal peptide, produced from inactive 81-kDa form by proteolysis at the carboxyl-terminal region. Replacements of Glu(115) and Asp(176), highly conserved residues in the family 8 glycosylase region, with Gln and Asn caused simultaneous loss of chitosanase and glucanase activities, suggesting that these residues formed part of the catalytic site. Truncation experiments demonstrated indispensability of an amino-terminal region spanning 425 residues adjacent to the signal peptide.
